Towards the next generation of mobile and wireless networks, machine-type communications (MTC) is expected to play a significant role and form the basis for the future Internet of Things (IoT). M2M communications offer a wide range of applications providing various services, such as the Smart Grid, the E-health system, Vehicle-to-Vehicle (V2V) communications, and etc. In the rest of the present description, all these kinds of wireless communication devices, such as e.g. wireless M2M communication devices are called “devices”. With the rapid growth of the M2M market, the number of devices in a wireless communication network can be tremendously increased and can potentially be very large, thus posing significant challenges to current radio access networks.
Once a transmission is triggered by a random event, for instance a malfunction in the power network, the device needs certain wireless resources for its transmission. If a contention-free scheme is applied, a certain amount of dedicated resource blocks will be preserved for the transmissions, and the devices will access those resources in a coordinated manner. However, these kinds of schemes may lead to excessive signaling overhead between the devices and inefficient use of the reserved resource blocks. Moreover, since the wireless resources are in general very limited, those schemes scale poorly with the increasing amount of devices deployed in the network.
Therefore, for devices which need to access the network randomly, they can start with sending a resource request to the network in order to indicate their active status and request for the uplink/sidelink resources for their transmission. A general schematic example of a wireless communication network with a base station (BS) 1 and a plurality of wireless communication devices 2 is shown in FIG. 1. In the example of LTE and LTE-Advance, which is also an example of potential implementation of the disclosure, the random access (RA) procedure comprises four steps as shown in FIG. 2.
Step S1: A device 2 transmits a randomly selected RA preamble sequence on the Physical Random Access Channel (PRACH) to the base station 1.
Step S2: The base station 1 transmits an RA response on the Physical Downlink Shared Channel (PDSCH) in respond to the detected preamble sequence.
Step S3: The device 2 transmits its identity and other messages, e.g., a scheduling request to the base station 1 using the uplink/sidelink resources assigned in the RA response in the second step S2.
Step S4: The base station 1 echoes the device identity it received in the third step on PDSCH.
The base station 1 does not necessarily to be the real entity of a macro/micro base station, but also can be any kind of a central controller for resource allocation and network management. All these functional and/or physical entities which perform the relevant functions are called “base station (BS)” in the rest of the present description of the background as well as the various aspects and embodiments of the present disclosure.
According to the LTE specifications, each cell is assigned a pool of 64 Zadoff-Chu sequences as preambles for the Step S1 transmission. However, a collision will occur if two or more user equipments (UEs), i.e. devices 2, have randomly selected the same preamble. When the number of accessing devices 2 becomes excessively large, the simultaneous access attempts will incur a high probability of collisions in the first step of the random access, since the number of preambles and the Random Access Channel (RACH) resources are quite limited. Hence, the RA procedure scales poorly with the increasing number of devices 2 in the network and the network will easily become overloaded and congested, leading to high detection failure rate and large access delays.
The massive deployment of devices in the MTC network poses significant challenges to the current radio network in term of device detection and resource allocation, especially when the devices access the network randomly. Seamless coordination and excessive information exchange between the devices are required by conventional access schemes to mitigate collisions in the random access channel, which leads to immoderate signaling overhead.
The object of the present disclosure is therefore to propose a mechanism, and specifically wireless communication devices, a base station and a method for resource allocation for a wireless communication network comprising a plurality of wireless communication devices and a base station, in which the signaling overhead for resource allocation is reduced and a faster and more efficient resource access is provided.